Sleepiness is a rising issue when a person is tired, and it typically occurs when a person works for a long period of time and that easily raises dangerous situation.
For example, long time driving, more specifically night time driving alone, can easily make one sleepy, but there is no way to prevent the sleepiness except for short rest or sleep. However, most vehicle drivers usually drive without enough rest or sleep because of their intensive work, and therefore the frequency of vehicle accidents has not decreased.